Probabilistic Approach to Evaluate Acceptable Toll Rates in Road Concessions

Abstract

Countries worldwide make substantial efforts to keep the condition of their road infrastructure at an acceptable level under budgetary constraints. One possible model that enables the delivery of road projects under limited budgets is a public-private partnership (PPP). Because of several technical, financial, legal, and economic issues that need to be addressed, PPP agreements are relatively complex. In addition, defining long-term rights and obligations between the public sector and the private concessionaire requires an in-depth risk analysis because of the considerable number of risks usually encountered in PPP projects, such as a toll road concession. The objective of this paper is to present a method for an ex ante assessment of the acceptable toll rate for different stakeholders based on a probabilistic analysis of construction costs, operations and maintenance costs, and traffic volumes. The financial constraints included in the analysis are the debt service coverage ratio and return on equity. The resulting toll rates are determined from the simulated probability distributions of the input parameters. Such rates are then compared with the socially acceptable toll rate. The application of the proposed method to a case study of a toll road concession in Greece for which publicly available data were obtained indicates that the method presented is able to capture some uncertainties and improve the project's risk quantification process. It is recommended that the proposed method be tested on other projects for further validation and eventual upgrading of the model for use as a tool in risk management in toll road concessions.